Photochemistry of radical ions with irradiation of electron and laser pulses

Photophysical and chemical properties of radical ions of aromatic compounds in the excited states已被clarified by a pulse radiolysis-laser flash photolysis combined method. The lifetimes ofradical cations and anions of cis- and trans-stibene (c-St and t-St) and radical anions ofdicyanoanthracene, phenazine,and anthraquinones in the excited states measured for the first time and their transient and anthraquinones in the excited states were measured for the first time and their transientphenomena such as the photoelectron ejection, c-t isomerization，and selective hole and electron transfer quenching of the radical cations and anions in the excitedstates, respectively,investigated. In the deactivation of radical cations of c-St In the excited doublet state(c-st ^ < * + * * >),the internal conversion competes with the isomerization to t-St^<*+> in a quantum yield of 0.49，whereas t-St^<*+**> is only deactivated via internal conversion. Lifetimes of t-St^<*+**> andc-St <*+**> are estimated to be approximately 240 and 120psrespectively. The shorter lifetime of…c-St^<*+**> is attributed to isomerization and conversion to another product viatwisting about the central C=C double bond. St radical anions in the excited doublet state（St^<*-**>） undergo unimolecular isomerization from c-St^<*-> to t-St^<*->, photoelectron ejection，and electron transfer to biphenyl added as a quencher. From the selective electron transfer FromSt^<*-**> to biphenyl （Bp）the lifetimes of c-St^<*-**> and t-St^<*-**> are estimated to be approximately 1.5 and 2.5 ns，respectively. The shorter tau of c-St <*-**> is attributed to isomerization via twisting about Thecentral C=C double bond. The tau values of C - st ^<*-**> and t-St^<*-**> are 1 order of magnitudelonger than those of c-St^<*+**> and t-St^<*+**>. Lifetimes of approximately 4 ns are estimated forM^ *-**> (M=dicyanoanthracene, phenazine，The shorter lifetimes of 1.0-1.4 ns for methyl and chloro substituents onanthraquinone are explained in terms of internal conversion accelerated by rotatio of thesubstituents. The energy gap between The excited and ground states of M . is a singnficant factorfor the rate of the internal conversion. A solvated pair of M and quencher是suggested as anintermediate in the electron-transfer quenching of M^<*-**> by quencher such as fumaronitile. Less

Photophysical and chemical properties of radical ions of aromatic compounds in the excited states have been clarified by a pulse radiolysis-laser flash photolysis combined method. The lifetimes of radical cations and anions of cis- and trans-stibene (c-St and t-St) and radical anions of dicyanoanthracene, phenazine, and anthraquinones in the excited states were measured for the first time and their transient phenomena such as the photoelectron ejection, c-t isomerization, and selective hole and electron transfer quenching of the radical cations and anions in the excited states, respectively, were investigated. In the deactivation of radical cations of c-St in the excited doublet state (c-St^<*+**>), the internal conversion competes with the isomerization to t-St^<*+> in a quantum yield of 0.49, whereas t-St^<*+**> is only deactivated via internal conversion. Lifetimes of t-St^<*+**> and c-St^<*+**> are estimated to be approximately 240 and 120 ps, respectively. The shorter lifetime of … More c-St^<*+**> is attributed to isomerization and conversion to another product via twisting about the central C=C double bond. St radical anions in the excited doublet state (St^<*-**>) undergo unimolecular isomerization from c-St^<*-> to t-St^<*->, photoelectron ejection, and electron transfer to biphenyl added as a quencher. From the selective electron transfer from St^<*-**> to biphenyl (Bp), the lifetimes of c-St^<*-**> and t-St^<*-**> are estimated to be approximately 1.5 and 2.5 ns, respectively. The shorter tau of c-St^<*-**> is attributed to isomerization via twisting about the central C=C double bond. The tau values of c-St^<*-**> and t-St^<*-**> are 1 order of magnitude longer than those of c-St^<*+**> and t-St^<*+**>. Lifetimes of approximately 4 ns are estimated for M^<*-**> (M=dicyanoanthracene, phenazine, and anthraquinones). The shorter lifetimes of 1.0-1.4 ns for methyl and chloro substituents on anthraquinone are explained in terms of internal conversion accelerated by rotatio of the substituents. The energy gap between the excited and ground states of M^<・-> is a singnficant factor for the rate of the internal conversion. A solvated pair of M and quencher^<・-> is suggested as an intermediate in the electron-transfer quenching of M^<*-**> by quencher such as fumaronitile. Less